The present invention relates to a method for simultaneously forming radially extending tooth grooves at two points in an end face of an annular portion of a work by grinding using a cup-shaped grindstone having an axis offset from an axis of the work, while indexing the annular portion through a predetermined angle at a time by an indexing board.
A method and apparatus for producing a CURVIC Coupling(trademark) are known from Japanese Patent Application Laid-open No. 2000-52144. The CURVIC Coupling(trademark) includes a first member having radial tooth grooves defined in an end face of an annular portion. A second member has radial tooth grooves defined in an end face of the annular portion, so that both of the first and second members are coaxially coupled by the tooth grooves of the former and the tooth grooves of the latter with each other. In this case, convex tooth ridges 5 and concave tooth grooves 4 of the second member (see FIG. 15B) are tightly engaged with the convex tooth grooves 4 and the concave tooth ridges 5 of the first member (see FIG. 15A) to illustrate a self-alignment function.
To form the tooth grooves for the Curvic Coupling(trademark), a cup-shaped face mill is used. An axis of the cup-shaped face mill is parallel to and offset from an axis of an annular portion of a work (a first member or a second member). The end face of the annular portion is simultaneously ground at two points by cutting by the cup-shaped face mill while indexing the work through a predetermined angle. Finally, a large number of tooth grooves are roughly finished at predetermined distances in the entire periphery of the annular portion. Then, the cup-shaped face mill is replaced by a cup-shaped grindstone of CBN, and the above-described step is repeated to finish the roughly finished tooth grooves by the cup-shaped grindstone of CBN.
The conventionally known apparatus suffers from the necessity of having to replace the cup-shaped face mill with the cup-shaped grindstone of CBN, thereby resulting in an extended manufacturing time.
Another drawback is the necessity of having to supply a cooling liquid to cool the grinding faces of the cup-shaped face mill and the cup-shaped grindstone of CBN from the outside. Accordingly, the cooling liquid is unable to adequately reach the grinding faces, resulting in a reduced durability of each of the cup-shaped face mill and the cup-shaped grindstone of CBN.
It is an object of the present invention to overcome the above-described drawbacks of the related art.
It is another object of the present invention to ensure that to form tooth grooves in an end face of an annular face of a work by grinding, the tooth grooves can be made by the grinding without replacement of a tool, and the cooling of the tool can be promoted, leading to an enhanced durability of the tool.
It is yet another object of the present invention to provide a method for forming tooth grooves, which includes supporting a work having an annular portion, so that its axis is aligned with an axis of an indexing board, and radially extending tooth grooves are simultaneously formed in an end face of the annular portion at two points in a grinding manner using a cup-shaped grindstone having an axis offset from the axis of the work, while indexing the annular portion through a predetermined angle at a time by the indexing board. The method includes a rough-finish processing step that cuts the tooth grooves by intermittently feeding the cup-shaped grindstone in a predetermined amount at a time. A finish processing step finishes of the tooth grooves by retaining the cup-shaped grindstone at a predetermined position after the rough-finish processing step, while supplying a cooling liquid from cooling-liquid ejecting bores defined in at least one of grinding faces of the cup-shaped grindstone during each of the steps.